Thank you all for your replies but my main question 'Does the KC135 boom have the facility to lock into the receiver's refuelling receptacle?' remains unanswered. I assume that this facility must exist in some form in order to be able to tow but surely there must be some form of weak link in the boom assembly to protect the boom assembly (and the tanker) if the load becomes excessive. Clearly this facility is one advantage over the probe/drogue system. .